11.   Just over half read a staff summary of their mail from constituents daily or weekly, while the rest ask for reports on selected topics or at irregular intervals.

12.   Masked guards would deliver meager food rations at irregular intervals, and periodically move their prisoners to different locations, always at night.

13.   The strange thing is that at irregular intervals, all the caterpillars suddenly twitch at the same time!

14.   The two phenomena constantly alternate back and forth, following each other at irregular intervals.

15.   This is the expanse of warm water that every few years, at irregular intervals, spreads eastward along the Equator from the western Pacific to South America.

16.   Runners in the marathon complained that refreshments were served at irregular intervals.

17.   The Air Force has had an acute problem with pilots leaving for commercial aviation, in part because of dissatisfaction with deploying abroad for long periods at irregular intervals.

18.   The disease affects the nervous system and gradually impairs motor control, with symptoms appearing at irregular intervals for years.

19.   Government ministers would from now on meet every week instead of only at irregular intervals.

20.   Supervision would be carried out at irregular intervals and focus on major cases, the official said.